Training ammunition cartridge with a gaseous plume signature

ABSTRACT

A training ammunition projectile has a solid chemical component disposed in a base compartment that produces a gaseous visible plume after impact. The ammunition cartridge generates kinetic energy while propelling the projectile through a weapon barrel. This firing process imparts heat into a projectiles driving band. When the projectile is in flight, heat passes from the projectile&#39;s driving band into a compartment in the projectile housing the chemical component. When the component is exposed to increasing heat and low pressure, the it undergoes rapid sublimation. The projectile is configured with a vent opening in its base for emergence of the gaseous plume during flight. The opening is preferably capped to allow for stable storage and to prevent any gas from escaping until the projectile is fired.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Provisional Patent Application No. 61/803,827, filed Mar. 21, 2013.

BACKGROUND THE INVENTION

The present invention relates to the field of training ammunition and, more specifically, to a non-pyrotechnic training ammunition cartridge having a projectile that can mark its flight path as well as its point of impact both by day and by night.

Military gunners often fire their weapons at long range in military training areas that include grass, vegetation and low lying trees. Hence, while there is some value in firing projectiles that directly mark a target on impact, the morphology and terrain on a military range frequently preclude gunners from having direct views the actual impact points.

Good military training devices should simulate the effects of live fire high-explosive detonations. In combat such detonations generate visual and near infra-red light and heat, forming a multi-spectral signature. High explosive detonations also produce smoke plumes. The light and heat resulting from high-explosive detonations can be detected by an array of fire control deices used by the military. The smoke plumes are also visible to the naked eye.

The target locating devices used in the military have visual cameras and cameras that operate in the near and/or far IR spectrum. Accordingly it is desired that practice ammunition simulate the effects seen in combat and that practice ammunition generate multi-spectral marking signatures upon impact that can be viewed by these cameras.

Currently, military forces use a wide array of technologies to detect and identify targets and adjust fire. Traditionally, they have used pyrotechnic devices in training ammunition allowing gunners to trace their fire and mark their targets. These pyrotechnic devices produce smoke and heat plumes from combustion of pyrotechnic compounds. Unfortunately, the devices have often resulted in unexploded ordnance (UXO) which is dangerous and expensive to clean up. Pyrotechnic devices can also start range fires that destroy the environment.

To prevent the generation of UXO and range fires during training, inert practice ammunition cartridges have been developed which do not employ energetic pyrotechnics to trace the flight and mark the impact of the projectile. For example, low density, dry fine powders have been used to create a plume for visibly marking the target upon impact.

Chemi-luminescent technology, such as that taught in the U.S. Pat. No. 6,819,211, has also been used to mark both the trace and point of impact by night. There are, however, certain drawbacks to this technology as currently practiced: Currently available chemi-luminescent materials do not work well at low temperatures and do not generate enough heat to provide a good signature for thermal weapon sensors. Further, when used to illuminate a projectile trace, the head (ogive) of the projectile which houses the chemo-luminescent material must be made of a transparent or translucent plastic.

The U.S. Pat. No. 8,438,978 discloses a multi-spectral marking projectile having chemical components that are caused to mix upon setback, due to the initial acceleration and the centrifugal forces, and produce an exothermic reaction to emit heat during the flight of the projectile. This serves to warm the chemi-luminescent materials during flight and provides an Infrared marking signature when the projectile strikes the target.

The U.S. Pat. No. 7,055,438 also discloses a flameless tracer/marker utilizing heat marking chemicals in addition to chemo-luminescent materials.

The U.S. Pat. No. 8,443,732 discloses multi-spectral marking projectile which mixes and heats chemi-luminescent materials during flight and expels them under pressure when the projectile striker a target.

The subject matter of the various patents noted above is incorporated herein by reference.

SUMMARY OF THE INVENTION

The principal objective of the present invention is to provide a non-pyrotechnic ammunition cartridge with a training projectile that closely simulates the effects of live fire detonations on impact and creates and marking plumes for the ammunition that may be detected by optical deviates, military night vision and thermal sensors.

A further objective is to provide a training projectile of this type which overcomes the drawbacks of the known projectiles disclosed in the prior art.

A still further objective of the present invention is to provide a training projectile of this type having a configuration that may be manufactured at a reasonable cost.

These objectives are achieved, according to the present invention, by providing a training projectile with a solid chemical component disposed in a base compartment, that produces a gaseous visible plume for tracing the projectile in flight. The chemical component is selected to sublimate and form a gas when heated during firing of the projectile. The projectile is configured with an opening in its base for emergence of the gaseous plume during flight. The opening is preferably closed with (1) a cap that is ejected by the gas pressure resulting from sublimation, (2) a combustible cap that ignites and burns with the cartridge ignition, or (3) a cap made of a plastic that vaporizes when exposed to the hot burning gases created during the cartridge ignition.

The ammunition projectile generates kinetic energy while passing through the barrel of the weapon. This firing process imparts heat into the projectile's driving band. When the projectile is in flight, heat passes from the driving band into a compartment in the rear of the projectile that houses the solid chemical component. When the component is exposed to increasing heat and low pressure, it undergoes rapid sublimation.

The solid chemical component may be any chemical element or compound which sublimates to a visible gas at elevated temperatures in the range of 4° to 120° C. An example of such a component is iodine, a chemical element which produces a gas with a violet hue.

The training projectile is preferably also provided with uniquely positioned constituent chemi-luminescent materials contained in a fragile matrix fitted against the inner surface of head of the hollow projectile (ogive). These chemi-luminescent components can either survive “set back” and remain intact until impact, or be released and allowed to mix and luminesce upon firing due to the initial acceleration and the centrifugal forces acting on the projectile. In the latter case, the chemo-luminescence can be used to trace the flight of the projectile as well as to mark the point of impact.

The projectile harvests heat from the friction imparted to the projectile's driving band when fired from a weapon, transferring heat into an optimized heat sink configuration. As heat is transferred to the projectile body, it is conducted into both the (1) chemi-luminescent constituents and (2) the solid material which sublimates at an elevated temperature. During flight a vapor trail commences as the solid material, adhering to a heat sink, sublimates releasing a gas plume. The vent opening in the rear of the projectile is configured to minimize disturbance of the projectile in flight.

The projectile body includes a cavity, preferably near the vent opening in the rear, to store the solid chemical component. Function fire (at setback) of the cartridge generates significant heat that is transferred into the projectile body. A heat sink type design transfers heat from the exterior of the body to the chemical component causing sublimation.

By locating the vent in the rear of the projectile, sublimation is accelerated because the ballistic flight creates a low pressure void at the rear of the projectile. The low pressure generated in flight initiates quick and reliable sublimation of the material. As heat passes from the driving band to the compartment containing the sublimating material, the process continues even while the projectile slows and the pressure at the vent increases. By the time the projectile strikes a target the sublimation process continues generating a distinct marking plume visible in the UV, Visual, near IR and Far IR spectrum.

Iodine is one such chemical that undergoes a phase change from a solid to a gas (sublimation) at elevated temperatures. Iodine gas has a violet hue that can create a visible plume. Use of a solid (rather than a liquid) material that undergoes a direct solid-to-gas phase change provides for good ballistic flight stability.

If additional heat is required to cause sublimation, depending upon the solid chemical component used, a plurality of second chemical components may be provided, housed in additional compartments in the projectile and released during setback due to the initial acceleration and/or the centrifugal forces acting on the projectile when the projectile is fired. These second components are selected to react chemically exothermally when mixed, causing them to heat the solid chemical component to its sublimating temperature.

These second chemical components may be housed in frangible compartments in the projectile head which are designed to burst when the projectile body strikes a target. In this way the second components will create a plume for Infrared marking of the target upon impact.

The second components may, for example, comprise a metallic powder that, when exposed to air or oxygen, creates an exothermic reaction. The air or oxygen may be provided in gaseous form or as either a solid or liquid oxide.

To prevent damage from overheating, a third chemical component may also be provided, disposed in a third compartment in the projectile, which is designed to undergo a phase change at a prescribed temperature, e.g., by melting. This third component can serve to absorb thermal energy at a prescribed temperature and thereby prevent overheating of the projectile and the marking agents during flight.

Further marking agents may also be provided in projectile head, which is designed to burst when the projectile body strikes a target. As is conventional, a fine dry powder may be housed in a separate compartment in the projectile head to create a plume for visible marking of the target upon impact.

For a full understanding of the present invention, reference should now be made to the following detailed description of the preferred embodiments of the invention as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a phase change diagram for iodine.

FIG. 2 is a cutaway view of a projectile according to the invention containing a solid marking agent in a rear compartment.

FIG. 3 shows how heat is harvested in a projectile from friction and propellant gases.

FIG. 4 is an image depicting heat sinks and a vent at the rear of a projectile.

FIG. 5 is a representational diagram of the projectile according to the invention with a cap removed upon ignition and with a vapor plume emanating from the rear.

FIG. 6 is cutaway view of a projectile showing two “bubble wrap” type sheets arranged adjacent the inner surface of the projectile head, the sheets having a large number of frangible bubble-shaped compartments containing chemical components for marking the point of impact.

FIG. 7 is a representational diagram showing a low pressure area at the base of a subsonic projectile in flight.

FIG. 8 is a representational diagram showing a low pressure area at the base of a supersonic projectile in flight.

FIG. 9 is a representational diagram of a projectile according to the invention having multiple compartments for marking agents.

FIG. 10 is a representational diagram showing a vapor plume emanating from the projectile of FIG. 9 while in flight.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will now be described with reference to FIGS. 1-10 of the drawings. Identical elements in the various figures are designated with the same reference numerals.

According to the present invention, both the trace and point of impact of a projectile can be marked by a plume generated by sublimation of gaseous fumes at elevated temperatures from a solid material such as iodine. In the case of iodine the sublimation is due to its special characteristics, illustrated by the phase diagram shown in FIG. 1. Iodine sublimates at temperatures lower than 113.6° C. (Celsius) due to its low vapor pressure.

In addition to or in place of iodine colored organic dyes of the type used in signaling colored smoke grenades may be used as a marking agent. Some of these dyes are based on anthraquinone and are widely available in a range of colors in the dyestuff industry. In smoke grenades, an exothermic pyrotechnic reaction is used to volatilize and sublime the colored dyes. As explained below, several mechanisms are available to generate heat to raise the temperature of the projectile to a desired level during flight.

FIG. 2 shows a training projectile 10 having a rear chamber 14 housing a solid chemical component 11, such as iodine. In flight, the projectile vents sublimated iodine gas through an orifice 13 at the central point of the base. The chamber 14 housing the solid iodine is sealed by a cap 16 when the projectile is in storage, precluding and preventing loss of the iodine due to evaporation. Once the projectile and storage chamber are heated after set-back, the cap 16 either burns or is ejected, releasing the iodine gas. The re-circulating free flow of air in the base—that is, the turbulent wake of the projectile in flight—creates a region of low pressure of less than one atmosphere. This low pressure starts the sublimation of iodine and, by the time the projectile reaches it point of impact, the heat has created a detectable plume.

The training projectile cartridge “harvests” the heat generated during setback by the propellant gases and by friction with the barrel of the weapon. This process is illustrated in FIG. 3. Heat continues to be generated during flight of the projectile due to air friction and wake turbulence. This process is illustrated in FIGS. 7 and 8.

FIG. 4 shows the rear chamber 14 of the projectile 10 without the solid chemical component. To optimize heat transfer to the sublimating solid material, heat sinks 18 are provided in the rear projectile body.

As shown in FIG. 5, the cap 16 is removed upon ignition allowing a vapor plume 24 to escape through the orifice 13.

In addition to a vented compartment to store a sublimating material (e.g., iodine) the projectile 10 may include liquid reactive chemical luminescent materials contained in a plastic matrix, configured as a “bubble wrap” 30 and layered adjacent to the inner surface of the forward ogive as shown in FIG. 6. This “matrix packaging” configuration precludes shifting of the liquids which disturbs the flight characteristics of the projectile. The constituent chemi-luminescent materials mix on impact, partly adhering to the ogive and generally releasing into the atmosphere, forming a visual and IR signature visible at night or through near IR night vision devices.

The projectile may also contain a fine dyed powder in a separate compartment 32 that is released on impact for visual (day) marking.

FIG. 7 illustrates the low pressure at the tail of a projectile in subsonic flight resulting from the air passing over the body of a projectile. FIG. 8 shows the same for supersonic flight. As noted above, the sublimation point of iodine depends on both atmospheric pressure and temperature. The atmospheric pressure at the base (vent area) of a 40 mm cartridge traveling subsonic speed (240 m/s) will be about 0.95 atmospheres. With a .50 cal cartridge traveling supersonic speed, the atmospheric pressure at the projectile base (vent area) will drop to about 0.65 atmospheres. Either drop in pressure promotes sublimation. With supersonic speed the solid material sublimates quicker.

FIG. 9 is a representational diagram of a mortar round 10 which houses the markers according to the present invention. To this end, the mortar comprises a plurality of compartments A, B, C, D and E, as many as needed, arranged in sequence and housing various ones of the chemical components described above which are used in marking the ballistic flight and the impact point of the projectile. The compartment A at the rear of the projectile is the chamber 14 housing the solid chemical 11 that sublimates and forms a plume. The chamber 14 has a vent opening provided with a protective cap 16 that is removed when the projectile is fired, thereby permitting the gaseous plume to exit during the ballistic flight.

As shown, the mortar 10 has an ogive 12 and a tail fin 19 attached to the rear end 20 of the body for flight stability.

FIG. 10 illustrates the ballistic flight path of the mortar 10 and indicates the gaseous plume 24 released during flight. Upon impact, the ogive 12 of the mortar breaks apart releasing the various day and night markers contained in the compartments B, C, D and E. Details of this type of mortar may be found in the U.S. Pat. No. 8,443,732, the subject matter of which is incorporated herein by reference.

The present invention thus concerns a projectile with a frangible hood that can be configured in multiple calibers (with differing trajectories, spin rates, etc.). Upon impact, the impact pressure breaks open the ogive and chemi-luminescent and/or exothermic heat-generating components mix and provide a night and near IR signature. The release of a vapor from sublimating iodine creates a plume above the impact point that is visible in the daytime and from thermal devices.

There has thus been shown and described a novel training ammunition cartridge with a gaseous plume signature which fulfills all the objects and advantages sought therefor. Many changes, modifications, variations and other uses and applications of the subject invention will, however, become apparent to those skilled in the art after considering this specification and the accompanying drawings which disclose the preferred embodiments thereof. All such changes modification, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention, which is to be limited only by the claims which follow. 

What is claimed is:
 1. A training ammunition cartridge comprising a hollow projectile and a cartridge case with a propellant charge, the projectile having a hollow projectile body and a projectile head designed to withstand the forces applied when the projectile is fired from a gun and designed to burst when the projectile strikes a target, said projectile body having a projectile base with a compartment therein and further comprising: a solid first chemical component disposed in the base compartment of the projectile which sublimates and forms a gas when heated to an elevated temperature during firing and flight of the projectile, said projectile body having an opening in said base for emergence of the gas for marking the trail of the projectile by means of a gaseous visible plume during flight.
 2. The training ammunition cartridge defined in claim 1, wherein the elevated temperature is in the range 40° to 120° C.
 3. The training ammunition cartridge defined in claim 1, wherein the first chemical component is iodine.
 4. The training ammunition cartridge defined in claim 1, further comprising a closure disposed in said opening in the projectile base to prevent the emergence of the first chemical component prior to firing the projectile, said closure being configured to open and allow emergence of the first chemical component upon firing of the projectile.
 5. The training ammunition cartridge defined in claim 1, further comprising a plurality of second chemical components each received in a respective second compartment in the projectile body, said second components being designed to react chemically exothermally when mixed, due to at least one of the initial acceleration and the centrifugal forces acting on the projectile as the projectile is fired from a weapon, causing the mixed second components to heat the first chemical component during flight of the projectile.
 6. The training ammunition cartridge defined in claim 5, wherein said projectile has a frangible ogive in the projectile head designed to burst when the projectile body strikes a target and wherein said second compartment is disposed in said head and such that said second components create a plume for Infrared marking of the target upon impact.
 7. The training ammunition cartridge defined in claim 5, wherein one of said second chemical components is a gas that includes oxygen.
 8. The training ammunition cartridge defined in claim 5, further comprising a third chemical component, disposed in a third compartment in the projectile body and designed to undergo a phase change at a prescribed temperature, said third chemical component serving to absorb heat at a prescribed temperature and thereby prevent overheating of the projectile and the marking agents during flight.
 9. The training ammunition cartridge defined in claim 8, wherein said third chemical component is a phase change material disposed within the projectile body, said phase change material being operative to melt and absorb thermal energy.
 10. The training ammunition cartridge defined in claim 1, wherein said projectile further comprises a marking agent disposed in the head for marking the position of the target upon release when the ogive has burst upon impact with the target, said marking agent comprising at least one of: (1) a plurality of fourth chemical components each received in separate fourth frangible compartment in the head, said fourth components being mixed and reacting chemically with each other when the compartments break, causing the mixed components to luminesce, said compartments being designed to be broken by at least one of the initial acceleration and the centrifugal forces acting on the projectile when the projectile is fired from a weapon, while retaining the fourth chemical components in the ogive so that such components are mixed at the time the projectile is fired from a weapon and luminesce by the time the projectile strikes the target; and (2) a fifth dry powder component disposed in the head and designed to create a plume for visible marking of the target upon impact.
 11. The train ammunition cartridge defined in claim 10, wherein the marking agent includes both (1) the fourth chemical components and (2) the fifth powder component for marking the target. 